1. Field of the Invention
The present invention relates to gear machining devices that machine a gear by a cutting process by synchronously rotating a machining tool and a workpiece at a high speed.
2. Description of the Related Art
Conventionally, one effective method to machine internal teeth and external teeth in the case of machining a gear by a cutting process using a machine tool such as a machining center is a machining method described in Japanese Patent Application Publication No. 2012-51049 (JP 2012-51049 A). This machining method is a machining method for creating teeth by a cutting process by synchronously rotating at a high speed a machining tool that is rotatable about a rotational axis, a cutter having, e.g., a plurality of cutting teeth, and a workpiece that is rotatable about a rotational axis tilted at a predetermined angle with respect to the rotational axis of the machining tool and feeding the machining tool in the direction of the rotation axis of the workpiece.
In this machining method, however, cutting resistance tends to be high since the plurality of cutting teeth contact the workpiece at the same time. Self-excited vibration therefore tends to occur during the cutting process, which may reduce tooth trace accuracy (tooth trace deviation) of the gear. Reducing the diameter of the machining tool can reduce the number of cutting teeth that contact the workpiece at the same time, but may reduce rigidity of the machining tool.
Japanese Patent Application Publication No. 2005-335061 (JP 2005-335061 A) describes a machining method in which a machining tool is moved in a direction of a feed path along the surface of a tooth of a workpiece. In this machining method, the machining tool is moved with respect to the workpiece at a varying feed speed in the direction of the feed path. According to this machining method, intervals between fine scratches that are made during machining are irregular along the surface of the tooth. Therefore, noise in a meshing part of the gear, namely self-excited vibration, can therefore be reduced.
In the machining method of JP 2005-335061 A, however, the feed speed of the machining tool with respect to the workpiece needs to be varied. This makes feed control complicated, making it difficult to improve accuracy of the tooth profile of the gear.